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ETCS (ERTMS)

The European Train Control System, part of ERTMS

1 - ETCS

European Train Control System

Context

The onboard computer of ETCS-enabled trains has to compute a number of position / speed curves. Here is how it works:

  • below all the curves, the speed indicator is white
  • above the indication curve, the speed indicator is yellow
  • above the permitted curve, the speed indicator is orange
  • above the warning curve, an alarm rings
  • above the intervention curves, an emergency break intervention is triggered

Inputs

In order to compute any of these curves, a number of things are needed:

  • target data (the destination of the braking curve, which can be EOA and SvL or LOA and MRSP)
  • train data
  • infrastructure data
  • infrastructure manager constants
  • standardized constants

Train

  • max speed
  • length
  • rotating mass
  • T_traction_cutoff: the time it take to cut off traction
  • braking model, either lambda or gamma:
    • lambda (braking weight/mass)
    • gamma (contant deceleration at a given speed)
  • correction factors (k_dry and k_wet for gamma braking) for braking curves

Infrastructure

  • corrected gradients (it incorporates curvature)
  • odometry balises location

Processes

Braking coefficients:

  • A_brake_emergency is the expected emergency braking capability, without safety margins
  • A_brake_safe is the emergency braking coefficient, with safety margins
  • A_brake_service is the expected service braking capability, without safety margins

Speed / distance targets

  • EOA end of movement authority: the location until which the train is allowed to move
  • SvL supervized location: the protected location

Curves

  • SBD supervised braking deceleration: intermediary result computed from EOA and A_brake_service
  • EBD emergency braking deceleration: intermediary result computed from SvL and A_brake_safe

All the curves below are cut below a given release speed:

  • EBI (emergency break intervention) computed from EBD, shifted in position and space given rolling stock metadata
  • SBI1 computed from SBD, shifted in time with Tbs1
  • SBI2 computed from SBD, shifted in time with Tbs2
  • FLOI (also called SBI, the intervention curve) the minimum of SBI1 and SBI2
  • WARNING (warning curve) computed as a shift of FLOI by Twarning
  • PS (permitted speed curve): shift of WARNING by time Tdriver
  • INDICATION is a shift of PS by time Tindication